The Viterbi decoder implements a soft-decision algorithm to demodulate digital data from an analog signal corrupted by noise. For the latter, FEC is an integral part of the initial analog-to-digital conversion in the receiver. FEC is widely used in modems and in cellular networks, as well.įEC processing in a receiver may be applied to a digital bit stream or in the demodulation of a digitally modulated carrier. Long-latency connections also benefit in the case of a satellite orbiting Uranus, retransmission due to errors can create a delay of five hours. įEC can be applied in situations where re-transmissions are costly or impossible, such as one-way communication links or when transmitting to multiple receivers in multicast. The American mathematician Richard Hamming pioneered this field in the 1940s and invented the first error-correcting code in 1950: the Hamming (7,4) code. The cost is a fixed, higher forward channel bandwidth. Therefore a reverse channel to request re-transmission may not be needed. The redundancy allows the receiver not only to detect errors that may occur anywhere in the message, but often to correct a limited number of errors. The central idea is that the sender encodes the message in a redundant way, most often by using an error correction code or error correcting code ( ECC). In computing, telecommunication, information theory, and coding theory, forward error correction ( FEC) or channel coding is a technique used for controlling errors in data transmission over unreliable or noisy communication channels. For the fiber-optic device, see optical interleaver.
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